The present invention relates generally to vehicle air conditioning systems and more particularly to variable refrigerant expansion devices for vehicle air conditioning systems that employ higher pressure, non-conventional refrigerants.
New regulations for refrigerants used in vehicle air conditioning systems are causing some vehicle air conditioning systems to employ refrigerants that operate at much higher pressures than conventional refrigerants used in vehicles. With these much higher pressures, the typical expansion devices used with the conventional refrigerants are not adequate. Accordingly, some have modified thermal expansion valves to operate at the higher pressures of the new refrigerants, but drawbacks exist with the diaphragm located in the thermal expansion valve between the inflow refrigerant stream and the outflow refrigerant stream and with a tube used for a temperature sensor, which is easily broken during assembly. Others have attempted to provide orifice tubes that can be used with the higher pressure refrigerants by providing a burst disk to protect an evaporator from overpressure and a bellows assembly coaxial with the orifice that is employed as a refrigerant bypass. But this orifice tube assembly is overly complex and expensive to fabricate and assemble. So it is desired to provide an expansion device capable of operating under the high pressures of newer vehicle refrigerants while providing for a relatively inexpensive and simple design that performs the desired functions.